The invention generally relates to superconducting flux-flow transistors. In particular, the invention relates to a double-sided high-temperature superconducting flux-flow transistor.
Prior art layered transistor structures have been known for some time, and although they offered many advantages in terms of numerous semiconductor applications, they still suffered from a number of disadvantages and shortcomings. One significant limitation with these layered transistor structures is the complex and multi-step layering fabrication process employed. This layering process often required deposition, patterning, a buffer layer and the need to match the superconductor on top of the buffer. Another limitation in prior art transistor structures is the significant difficulties caused by using a number of different materials in the complex multi-step layering process, particularly the fabrication and performance problems caused by varied dielectric constants in the different materials used.
Superconducting flux flow transistors provided several improvements over the prior art layered structures, but still suffered from the long-standing shortcoming of unwanted coupling of input-output signals. The unwanted coupling of input-output signals is associated with three terminal devices, such as the semiconductor and super-conducting flux flow transistors. In order to overcome the long-standing limitations, disadvantages and shortcomings of the layered and three terminal structures and to take advantage of mixed, or vortex state of High-Temperature ceramic superconductors, the present invention provides a double-sided superconducting structure that completely isolates the input and output from each other in separate patterned assembly structures. The advantageous double-sided structure eliminates the unwanted coupling of the input-output signals. In accordance with the present invention, each side of the substrate is patterned and chemically etched to provide a control-line assembly on one side of the structure that is opposed by a weak-link assembly, with the control-line assembly being patterned on the thicker substrate side. By employing this invention""s innovative split input-output arrangement, the long-standing drawbacks, limitations and shortcomings of prior art layered structures and three terminal semiconductors have been overcome and resolved.
It is one object of this invention to provide a split input-output arrangement with a double-sided high-temperature superconducting flux-flow transistor comprising a control line assembly and a weak-link assembly etched on opposite sides of a substrate.
It is another object of this invention to provide a mixer comprising a split input-output arrangement with a double-sided high-temperature superconducting flux-flow transistor comprising a control line assembly and a weak-link assembly etched on opposite sides of a substrate.
To attain these objects and advantages, a double-sided high-temperature superconducting flux-flow transistor is provided, comprising a control line assembly and a weak-link assembly advantageously placed on opposite sides of the substrate to form a double-sided assembly that controls line current on the input side of the substrate that causes generation of vortices on the weak link structure patterned on the substrate""s output side. Advantageously placing the two assemblies on opposite sides of the same substrate provides the operator with significant modulating capability for applications such as an amplifier or a mixer. Each side of the substrate is patterned and chemically etched to provide a control-line assembly opposed by a weak-link assembly, with the control-line assembly being patterned on the thicker substrate side. In one embodiment, a high-temperature, yttrium barium copper oxide (YBCO) material is deposited on a lanthanum aluminum oxide (LAO) dielectric substrate by the thin-film process and both sides of the substrate are patterned and chemically etched to form opposing control-line and weak-link assemblies. In this arrangement, the control-line assembly is patterned on the thicker input side, having a thickness of about 3000 xc3x85 that is above the penetration depth of the superconducting material. The weak-link assembly is patterned on the thinner output film side, which at about 2000 xc3x85 thick is thinner than the penetration depth of the superconducting material. The penetration depth of any particular material will vary according to that material""s properties, but in any event, the weak-link assembly will always be thinner than the penetration depth.
These and other features of the invention will become more apparent from the Detailed Description and the drawings. The scope of the invention, however, is limited only by the claims.